The Co2Z(Sr3Co2Fe24-xCrxO41) planar hexagonal soft magnetic ferrites with Cr substitution were prepared by solidstate reaction and their magnetic properties were studied. The phase composition of the sample was analyzed and the lattice constants of the sample were calculated. The morphological characteristics of the sample were analyzed by SEM. The hysteresis loops of the sample were measured. The experimental results showed that the lattice constants of the sample did not change much after Cr ion substitution. When the substitution amount x≥0.3, the Z phase began to decompose. When the substitution amount x≤0.2, the saturated magnetization of the samples increased with the increase of Cr3+ substitution, and the saturated magnetization decreased with the increase of Cr3+ substitution when x>0.2. It can be seen that the magnetic properties of Co2Z can be improved by adding appropriate amount of Cr ions.